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Vocabulary

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volcano- a weak spot in crust where molten material, or magma, comes to the surface

magma- a molten mixture of rock forming substances

lava- magma that reaches the surface

Ring of Fire- a major volcanic belt

island arc- a string of islands created by erupting volcanoes

hot spot- an area where magma from deep within the mantle melts through the crust like a blowtorch

Outline

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Volcanoes and Plate Tectonics=

• What is a Volcano?

  • weak spot in crust
  • spews out lava
  • volcanic activity adds rock to land

• Location of Volcanoes

  • 600 active volcanoes
    • more lie beneath the sea
  • volcanoes occur in belts
    • major belt= Ring of Fire
  • volcanic belts form along boundaries of Earth's plate
    • crust weak fracture at boundaries
  • most volcanoes occur along diverging plate boundaries

• Volcanoes at Diverging Plate Boundaries

  • form along mid- ocean ridge= diverging plate boundary
    • along ridge, lava pours out of cracks on ocean floor
• =Volcanoes at Converging Boundaries=
  • many volcanoes form near plate boundaries
    • oceanic crust returns to the mantle in boundaries
  • the crust melt= forms magma, rises toward surface
    • magma erupts as lava, and volcanoes formed
  • volcanoes occur on....
    • islands
    • near boundaries
      • older, denser, lower plate creates deep ocean trench
      • lower plate sinks into asthenosphere, and melts
    • melted plate forms magma
      • magma seeps upward through crust's cracks
        • magma breaks through ocean floor, creating volcanoes
          • volcanoes create string of islands= island arc
          • island arc's curve echo's deep ocean trench
            • major island arc= New Zealand, Japan, Indonesia, Carribean Islands, etc.
    • Subduction occurs where edge of continental plate collides w/ oceanic plate
      • collisions produced Andes Mt. volcanoes

• Hot Spot Volcanoes

  • some volcanoes formed from hot spots
    • hot spot= area where magma from deep within the mantle melts through crust
    • hot spots lie in middle of of continental or oceanic plates
  • volcanoes from hot spots not from subduction
    • hot spots also can form under continents

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